Shielded connector for preventing arcing and surface leakage



Jan. 30, 1968' A. o. ADAMS SHIELDED CONNECTOR FOR PREVENTING v ARCINGAND SURFACE LEAKAGE Filed Sept. 24, 1965 United States Patent SHIELDEDCONNECTOR FOR PREVENTING ARCING AND SURFACE LEAKAGE Andrew 0. Adams,Inglewood, Calif., assignor to Leach Corporation, San Marino, Califi, acorporation of Delaware Filed Sept. 24, 1965, Ser. No. 489,879

9 Claims. (Cl. 174151) This invention relates in general to terminalconnectors and more particularly relates to a new and improved shieldedelectrical terminal connector for preventing arcing at high altitudeareas and other low pressure areas.

Todays modern rocketry, satellites and high altitude aircraft haveproduced new critical requirements for electrical terminal connectorsfor the circuitry utilized in these devices. When such electricalcircuitry is placed in an aircraft or rocket, for example that achievesflights at altitudes in the range of 80,000 to 100,000 feet, the variouselectrical connections are subject to a critical alternating currentleakage at that altitude, in the form of arcing from the uninsulatedconnections to other uninsulated conductive materials. In electricalcircuits such as relays, the electrical connections are often made atterminal posts which are mounted in a sealed, airtight metal container.Adequate precaution must be taken to insure against arcing between suchterminal posts and any uninsulated areas of the container which housesthe electrical circuitry.

In the past, the prior art techniques for avoiding arcing have centeredprimarily around two different but related approaches. Each of theseprior art appoaches suffer from numerous disadvantages which are avoidedby the principles of this invention.

One typical prior art assembly utilizes a plurality of electricallyconductive terminal posts which are insulated form a container by aglass seal or any other suitable insulating material. To avoid anypossibility of leakage or arc-over between the terminal and thecontainer it has been customary practice to insulate the entire outersurface of the container by coating it with a ceramic substance of ahigh dielectric constant. The enamel is baked on the container at hightemperatures which tend to increase the fabricating problems for thecontainer and is an inefficient and costly operation.

In addition, this baked enamel surface is easily chipped and damaged.For example, the enamel coating is often chipped from the containersurface by assembly-line opstations, or worse yet when the electricalconnections are being made at the terminal posts after the componentcontainer is mounted in the aircraft. In either event, the chipped relaycontainer must be discarded or the entire component assembly discardedbecause each chipped area provides a direct exposure of material for ashort circuit arcing path between the electrical terminal post and thechipped area. This chipping is particularly objectionable when it occursduring the installation of a packaged component in the aircraft or otherequipment, because the entire component often is discarded and a new oneinstalled.

Attempts have been made in the past to eliminate this objectionableenamel surface and such attempts in general have proved unsatisfactory.One attempt has been to utilize an oversized collar of porcelain orrubber material that seats over and surrounds a major portion of theterminal connector. Experience has shown that this collar must extendwell above the surface of the container and it thus increases theover-all height of the container and terminal posts. Further, this typeof connection is cumbersome and does not alleviate the breakage probleminasmuch as the porcelain is often cracked when the electricalconnection is tightened down on the terminal post. Similarly rubbercollars deteriorate and split. Such cracks or splits provide directshorts from the post to the uninsulated metal container. Furthermore,this porcelain colla-r has in the past been soldered or otherwisefastened to the container structure and when cracked or otherwisedamaged the entire container must be discarded.

The foregoing disadvantages of the prior art are eliminated by theshielded terminal connector of this invention which provides a simple,rugged inexpensive connector which eliminates any surface leakage or gaparcing throughout all pressure areas, including the critical pressure atapproximately 80,000 to 100,000 feet. In accordance with the principlesof this invention, a shielded connector comprises a conductive terminalpost having an oversized landing that is housed in an insulatingmaterial held in an electrically conductive container. An elasticinsulating washer surrounds the landing and is seated over theinsulating material. A rigid disk having an aperture similar to thelanding is seated over the post and in contact with the washer, saiddisk includes a recessed area for receiving a nut threaded to theterminal post and contacting the landing area. The periphery of theinsulating disk, including a portion of the recessed area extend ingbeyond the threaded nut, defines sufiicient area of insulating materialfor shielding any arcing tendency between the post, the nut, and themetal container. In addition, the flanged area formed by the outsideperiphery of the disk and the recessed area in which the nut is recessedextends outwardly from the outer edge of the nut a sufficient distancethat the existing air gap between the outer edge of the nut and thenearest point on the container is greater than a critical arcing gap forthe electrical potential connected to the terminals. Various alternativeshapes of the insulated disk are provided as such shapes may be requiredfor different specified voltages under different operating conditions.With the new and improved terminal connector of this invention, shouldany breakage occur at the insulated disk there is no requirement thatthe container or components be discarded, as in the prior art, becausethe cracked shielding disk may readily be replaced by simply removingthe threaded nut and placing a new shielding disk over the terminalpost. The foregoing features and principles of this invention will morereadily be understood by reference to the accompanying drawing in which:

FIG. 1 is a top view of a terminal post in accordance with theprinciples of this invention;

FIG. 2 is a side elevation taken along line 2-2 into the paper of FIG.1; and

FIGS. 3 through 5 depict alternative configurations for the shieldingdisk of this invention.

FIG. 1 depicts a top view of the terminal connector 25 of thisinvention, an electrical conductor 5, and one portion of a container 10.It should be understood that a plurality of such terminals may exist ina container which houses electrical components. For example, container10 may house capacitors, relays, or numerous other electrical componentsrequiring electrical connections as part of their operation.

The terminal 25 of this invention includes a threaded post 11 which isinsulated and mounted in the container 10. A threaded nut 12 which maybe circular as shown, is threaded to mate with the threads of post 11.Nut 12 is threaded onto the post 11 and is seated in an annular recess13 of a rigid shielding disk 14. This disk 14 may be of any suitablerigid material which is a high dielectric such as moldeddiallylphthalate or Bakelite, or other similar insulating materialscharacterized by ease in forming and high impact resistance. r

The terminal connector 25 of this invention is shown in side elevationin FIG. 2 taken along the line 22 into the paper at FIG. 1. In FIG. 2the threaded electrically conductive post 11 is shown with a cylindricaloversized landing area 15 of suflicient depth to extend through theflange extensions 16 in container 10. This landing is bonded by a ringof insulating material 17 to the flange area 16 of container 10. Thisinsulating material 17 may be any well known insulator such as a glassseal or a ceramic material having a high dielectric constant and capableof forming an airtight seal. An elastic washer 18 which may be circular,as shown, and consisting of rubber or silicone-base material surroundsthe landing area 15 of threaded post 11 and seats over the insulatingseal 17. This washer 18 provides a shield blocking any are gap whichotherwise would exist through the air between the portion of landing 15that is above the insulator material 17 and the nearest metal flangearea 16 of container 10. Washer 18, in addition to blocking the arc gapfrom areas 15 and 16, blocks any surface leakage across the insulatingglass 17 when the terminal post is fully assembled and washer 18 iscompressively seated between the insulating material 17 and disk 14.Washer 18 also serves as an airtight seal, when compressed, to stop anyminute leaks which might be present in the glass insulating material 17At this point it should be understood that it is general practice incomponent packaging, to hermetically seal the container 10 so as to forman airtight chamber within the container that is subjected to apredetermined atmospheric pressure such as the pressure at sea level.This pressure is highly resistant to arcing and surface leakage, andthus the air gap and surface leakage problem solved by this invention ispresent only at the exposed upper terminals. Thus there is norequirement for the terminal connector of this invention to be employedon the inside of the container 10- unless that portion is notpressurized.

Shielding disk 14 is provided with an aperture substantially the same aslanding area 15 of threaded post 11. Disk 14 is seated over post 11 andrests against the upper surface of washer 18. A threaded nut 12, whichin this embodiment is circular, has a downwardly extending shoulder thatmatches the upper part of landing 15 of post 11. This circular nut 12threads tightly against landing area 15 as by a spanner wrench insertedin the indentations 21.

Circular nut 12 and post 11, including the oversized landing 15 are allof high electrical conductivity material such as stainless steel. Acopper core 9, shown in dotted lines, may run the full length of post 11to further enhance its conductivity characteristics, if desired. Theupper threaded surface of nut 12 includes a beveled shoulder 8 whichserves as a trench for solder or other material for preventing anyfurther turning or loosening of nut 12 when it has been seated withproper torque on post 11. Conductor 5 is compressively sandwiched to nut12 by fastening means 6 which may be another threaded nut. Other wellknown techniques for securing nut 12 to its fixed position are availableand may be employed. It is desirable, however, that nut 12 be removableif necessary to replace insulator 14, if it should become damaged insome way.

As the side elevation of FIG. 2 shows, the diameter of the circular nut12 is less than the inside diameter of annular recess 13 of shieldingdisk 14. This diameter difference is chosen to represent an area, whichcoupled with the remaining insulating area, is sufiicient to eliminateany surface leakage.

As mentioned hereinbefore, there are at least two possible leakage paths(shown symbolically by dashed line 22 and solid arrow 23) which must beblocked for suitable connector operation at the critical pressurementioned hereinbefore. One of these paths is the surface area pathshown by dashed lines 22. Disk 14 is shaped at its outer periphery toincrease the surface area path 22 by any desired amount such that forthe particular signal to be applied to terminal 25 of this inventionthere is sufiicient surface area of an insulated material to prohibitany surface area arcing even at critical pressures. The second arc path,consists of a direct line from any uninsulated portion of nut 12 to thenearest unshielded surface point of container 10. One such typicaldirect arc path which is blocked by this invention, is shown by thesolid arrow 23. This pat-h 23 extends from the upper corner surface ofcircular nut 12 to the nearest point on the uninsulated container 10.Are path 23 is also blocked, or shielded, by disk 14 having an outwardlyextending flange, or overhang, such that any possibility of arcing atpath 23 is impossible.

It is obvious that the shielding disk 14 may assume any desiredconfiguration depending upon the particular electrical requirements ofthe component to which electrical energy is to be supplied. Some ofthese many possible alternative shapes are shown in FIGS. 3 through 5.In FIGS. 3 through 5, there is a downwardly extending flange area 30 aswell as an upwardly extending flange area 31. This downwardly extendingflange 30 may be utilized to add further compression and confinement tothe elastic was-her 18 if such confinement is necessary to avoid arcingfrom landing 15 to container 10. Furthermore, this compressiveconfinement of washer 18 further enhances the sealing capacity to guardagainst minute pressure leaks in the insulator material 17, and providesprotection of Washer 18 from aging, splitting and deterioration.

In the disk 34 of FIG. 3 the outside edge 35 is a concave peripheralcurve around the circumference of disk 34. This concave groove 35increases the surface area available for any given diameter. In asimilar manner, the periphery 55 of insulator disc 54 of FIG. 5 isconvex to increase the amount of surface area for any given diameter. Arectangular peripheral circumference 45 is provided for the disk 44 ofFIG. 4 as another alternative shape.

It is to be understood that the foregoing features and principles ofthis invention are merely descriptive, and that many departures andvariations thereof are possible by those skilled in the art, withoutdeparting from the spirit and scope of this invention.

What is claimed is:

1. In a packaged electrical component, an improved electrical connectorfor supplying current at a high applied voltage through an aperture tothe interior of a hermetically sealed container having an unshieldedelectrically conductive outer surface, said electrical connector beingoperative for preventing electrical arcing including electrical surfaceleakage between the connector and the containers unshielded outersurface for the applied voltage at critical high-altitude atmosphericpressures to which the component may be subjected, said connectorcomprising an electrically conductive post, a compression sealinsulatively housing the post in an airtight seal to the aperture in thecontainer, an elastic washer of high dielectric material surroundingsaid post and shielding the surrounded area from electrical arcingbetween the surrounded area of the post and the unshielded surface ofthe container; a shielding disk of rigid insulating material surroundingthe post and spaced away from the unshielded surface of the container bybeing seated on the upper surface of the elastic washer; means forreceiving an electrical conductor seated within the recess in the uppersurface of the shielding disk and removably fastened into electricallyconductive contact with the post; said shielding disk having a recess inthe upper side forming a raised peripherally extending flange extendingoutwardly from the electrical conductor receiving means and overhangingthe mounting aperture of the container a spaced distance therefrom forinsulatively interrupting any are paths from the conductor receivingmeans to the container surface, and for presenting an insulating surfaceincluding said peripheral edge and the outer surface of said elasticwasher, interposed between said conductor receiving means and thecontainer of length sufiicient to insulatively interrupt any electricalsurface leakage paths between the current receiving means and thecontainer surface.

2. In a packaged electrical component, an improved electrical connectorfor supplying current at a high applied voltage through an aperture tothe interior of a hermetically sealed container having an unshieldedelectrically conductive outer surface, said electrical connector beingoperative for preventing electrical arcing including electrical surfaceleakage between the connector and the containers unshielded outersurface for the applied voltage at critical high-altitude atmosphericpressures to which the component may be subjected, said connectorcomprising a threaded post having an oversized landing, a ring ofinsulating material for sealing said post in an airtight seal to theaperture of the container with the oversized landing outwardly extendingabove the upper surface of the container, an elastic washer ofinsulating material surrounding the oversized landing and seated tocover the insulating material for enhancing the airtight seal whencompressed, a rigid shielding disk of insulating material having anaperture substantially equal to the oversized landing seated on saidelastic washer and having an annular recess in the unseated side, a flatcircular metal nut having a diameter less than the diameter of theannular recess threaded on the post and seated in said recess with adownwardly extending shoulder passing through the aperture in the diskand seated on said landing when said elastic washer is compressivelyloaded by said threaded nut, an electrical conductor coupled to saidpost at an upper surface of said circular nut, and an insulating surfacearea for preventing arcing and surface leakage between the circular nutand the unshielded surface of the container, said area formed by aportion of the insulating disk spaced from the container by the elasticwasher and extending outwardly beyond the outermost edge of the metalnut and insulatively interposed between the outermost edge of thecircular nut and the surface of the unshielded container nearestthereto.

3. In a packaged electrical component, an improved electrical connectorfor supplying current at a high applied volt-age through an aperture tothe interior of a hermetically sealed container having an unshieldedelectrically conductive outer surface, said electrical connector beingoperative for preventing electrical arcing including electrical surfaceleakage between the connector and the containers unshielded outersurface for the applied voltage at critical high-altitude atmosphericpressures to which the component may be subjected, said electricalconnector comprising an electrically conductive post extending through amounting aperture in the container and having an oversized landing onthe post formed by an oversized collar; a glass compression seal forinsulatively housing, in an airtight seal between the post and themounting aperture, said collar with the landing being exposed at theupper outside surface of the glass compression seal; an elastic washerof high dielectric material compressibly surrounding said post forshielding the post including said landing area from electrical arcingbetween the post and the nearest unshielded surface of the container,and covering the glass seal, for sealing any minute leaks in the glasscompression seal; a rigid shielding disk of insulating material havingan aperture larger than the post and being seatably spaced from theunshielded outer surface of the container by said elastic washer; aconductor receiving seat means removably secured to the conductive postand seated against the disk for compressing the elastic washer, saidseat means including a downwardly extending portion passing through theopening in the shielding disk and engaging the oversized landing of thepost to form a current-conductive path therewith; said shielding diskhaving a recess in the upper side forming a raised peripherallyextending flange extending outwardly and separated by an airspace fromthe seat means and overhanging the mounting aperture of the container aspaced distance therefrom for insulatively interrupting any are pathsfrom the conductor receiving seat means to the container surface, andfor presenting an insulating surface including said peripheral edge andthe outer surface of said elastic washer, interposed between said seatmeans and the container of length sufficient to insulatively interruptany electrical surface leakage paths between the seat means and thecontainer surface.

4. A connector in accordance with claim 1 wherein said conductive postis threaded and includes an oversized unthreaded portion which isinsulated from the metal container by said compression seal and extendsabove the area of insulation between the post and the container, andwherein said elastic washer is a resilient material having an openingfor receiving the upwardly extending oversized portion of the post.

5. A connector in accordance with claim 4 wherein said shielding diskhas an aperture in the recessed area substantially matching that of theoversized portion of the post, and wherein said means for receiving anelectrical conductor to said post includes a first threaded nut with adownwardly extending shoulder passing through the aperture of said diskand said elastic washer to join with the oversized portion when threadedon said post, said first nut of a thickness extending above the uppersurface of the disk, and a second threaded nut for compressivelysandwiching an electrical conductor between it and the first nut.

6. A shielded electrical connector in accordance with claim 5 whereinsaid first nut is circular and wherein said recess in said disk is alarger circular area for receiving said first nut with an annular airgap between the edge of the circular nut and the inner edge of theflanged area of the disk defined by the circular recessed area.

7. A shielded electrical connector in accordance with claim 6 whereinsaid flanged area of said disk has a round convex periphery.

8. A shielded electrical connector in accordance with claim 6 whereinsaid flanged area of said disk has a concave periphery.

9. A shielded electrical connector in accordance with claim 6 whereinsaid flanged area of said disk has a grooved periphery.

References Cited UNITED STATES PATENTS 2,346,162 4/1944 Hanopol 174-152X 2,550,112 4/1951 Fields 174153 2,897,472 7/1959 OBrien l74153 XFOREIGN PATENTS 1,009,425 3/1952 France.

LARAMIE E. ASKIN, Primary Examiner.

1. IN A PACKAGED ELECTRICAL COMPONENTS, AND IMPROVED ELECTRICALCONNECTOR FOR SUPPLYING CURRENT AT A HIGH APPLIED VOLTAGE THROUGH ANAPERTURE TO THE INTERIOR OF A HERMETICALLY SEALED CONTAINER HAVING ANUNSHIELDED ELECTRICALLY CONDUCTIVE OUTER SURFACE, SAID ELECTRICALCONNECTOR BEING OPERATIVE FOR PREVENTING ELECTRICAL ARCING INCLUDINGELECTRICAL SURFACE LEAKAGE BETWEEN THE CONNECTOR AND THE CONTAINER''SUNSHIELDED OUTER SURFACE FOR THE APPLIED VOLTAGE AT CRITICALHIGH-ALTITUDE ATMOSPHERIC PRESSURES TO WHICH THE COMPONENT MAY BESUBJECTED, SAID CONNECTOR COMPRISING AN ELECTRICALLY CONDUCTIVE POST, ACOMPRESSION SEAL INSULATIVELY HOUSING THE POST IN AN AIRTIGHT SEAL TOTHE APERTURE IN THE CONTAINER, AN ELASTIC WASHER OF HIGH DIELECTRICMATERIAL SURROUNDING SAID POST AND SHIELDING THE SURROUNDED AREA FROMELECTRICAL ARCING BETWEEN THE SURROUNDED AREA OF THE POST AND THEUNSHIELDED SURFACE OF THE CONTAINER; A SHIELDING DISK OF RIGIDINSULATING MATERIAL SURROUNDING THE POST AND SPACED AWAY FROM THEUNSHIELDED SURFACE OF THE CONTAINER BY BEING SEATED ON THE UPPER SURFACEOF THE ELASTIC WASHER; MEANS FOR RECEIVING AN ELECTRICAL CONDUCTORSEATED WITHIN THE RECESS IN THE UPPER SURFACE OF THE SHIELDING DISK ANDREMOVABLY FASTENED INTO ELECTRICALLY CONDUCTIVE CONTACT WITH THE POST;AND SHIELDING DISK HAVING A RECESS IN THE UPPER SIDE FORMING A RAISEDPERIPHERALLY EXTENDING FLANGE EXTENDING OUTWARDLY FROM THE ELECTRICALCONDUCTOR RECEIVING MEANS AND OVERHANGING THE MOUNTING APERTURE MEANS TOTHE CONTAINER SURFACE, THEREFROM FOR INSULATIVELY INTERRUPTING ANY ARCPATHS FROM THE CONDUCTOR RECEIVING MEANS TO THE CONTAINER SURFACE, ANDFOR PRESENTING AN INSULATING SURFACE INCLUDING SAID PERIPHERAL EDGE ANDTHE OUTER SURFACE OF SAID ELASTIC WASHER, INTERPOSED BETWEEN SAIDCONDUCTOR RECEIVING MEANS AND THE CONTAINER OF LENGTH SUFFICIENT TOINSULATIVELY INTERRUPT ANY ELECTRICAL SURFACE LEAKAGE PATHS BETWEEN THECURRENT RECEIVING MEANS AND THE CONTAINER SURFACE.